A retinotopic reference frame for space throughout human visual cortex

Abstract

SummaryWe perceive a stable visual world across eye movements, despite the drastic retinal transients these movements produce. To explain vision’s spatial stability, it has been suggested that the brain encodes the location of attended visual stimuli in an external, or spatiotopic, reference frame. However, spatiotopy is seemingly at odds with the fundamental retinotopic organization of visual inputs. Here, we probe the spatial reference frame of vision using ultra-high-field (7T) fMRI and single-voxel population receptive field mapping, while independently manipulating both gaze direction and spatial attention. To manipulate spatial attention, participants performed an equally demanding visual task on either a bar stimulus that traversed the visual field, or a small foveated stimulus. To dissociate retinal stimulus position from its real-world position the entire stimulus array was placed at one of three distinct horizontal screen positions in each run. We found that population receptive fields in all cortical visual field maps shift with the gaze, irrespective of how spatial attention is deployed. This pattern of results is consistent with a fully retinotopic reference frame for visual-spatial processing. Reasoning that a spatiotopic reference frame could conceivably be computed at the level of entire visual areas rather than at the level of individual voxels, we also used Bayesian decoding of stimulus location from the BOLD response patterns in visual areas. We found that decoded stimulus locations also adhere to the retinotopic frame of reference, by shifting with gaze position. Again, this result holds for all visual areas and irrespective of the deployment of spatial attention. We conclude that visual locations are encoded in a retinotopic reference frame throughout the visual hierarchy.